The Elevated Expression of FBP1, a Key-Enzyme of Gluconeogenesis Gene, Is Associated to High Sokal Risk In Chronic Myeloid Leukemia Patients.

Abstract 3399

The oncogenic transformation of Chronic Myeloid Leukemia (CML) cell of origin has been associated to an increased glucose metabolism, where the glycolytic pyruvate is directed away from the mitocondria, converted into lactate and secreted from the cell. This metabolic conversion is termed aerobic glycolysis, or Warburg effect and very essentially, it serves to support the tumor cell proliferation, by providing nucleotides, aminoacids and lipids enough to replicate all of cellular content. CML patients are historically stratified according to their Sokal risk score, which for more than 30 years has been regarded as the most significant prognostic factor in this hematological malignancies. The putative genetic and/or genomic basis driving this stratification are still not known.

Aim of the present study was to explore the molecular mechanisms associated to the CML patients stratification according to the Sokal risk score, by analyzing the transcriptome of the CD34+ cell fractions obtained at diagnosis from a cohort of high and non-high Sokal risk CML patients.

Overall, 67 patients with previously untreated CML in chronic phase (CP) entered the study; all of them have been enrolled in GIMEMA CML protocols and provided highly enriched CD34+ cell fractions from peripheral blood. Gene expression profiling (GEP) was performed, in order to identify genes most significantly and most differentially expressed between high and non-high Sokal risk patients. All other cases were used in Real-time experiments, in order to validate the GEP data.

By GEP, 82 probe-sets, corresponding to 78 genes resulted significantly differentially expressed between high and non-high Sokal risk patients in a supervised analysis of gene profiles. A gene enrichment analysis of this profile showed that genes involved in the Wnt, in the Notch signaling pathways and in the response to hypoxia and oxidative stress resulted significantly overexpressed in the comparison between high and non-high risk patients. We focused our attention on genes involved in the glycolysis and gluconeogenesis metabolic pathways (FBP1, SEPP1, GSTM3, GSTT1, PRDX2, MPO). We validated by Real-time the de-regulated expression of these genes in a different set of newly diagnosed CP-CML patients, thus confirming that they are differentially expressed between high and non-high risk patients, with trends similar to those observed by GEP. Particularly interesting resulted a significantly higher expression in high Sokal risk patients of FBP1 (fructose 1,6 bisphosphatase), a key-enzyme of gluconeogenesis, together with a significant over-expression of genes coding for enzyme involved in gluthatione biosynthesis (GSTM3, GSTT1, and PRDX2). These data suggest that CD34+ cells obtained from high Sokal risk patients might exhibit an unexpected moderation of the glycolytic flux, mainly due to the over-expression of FBP1, which might cause a re-direction of the pathway into the pentose phosphate shunt. A similar metabolic reprogramming has been already described in imatinib resistant bcr-abl positive cell lines and is supported also by the over-expression in high risk patients of G6PDH (Glucose-6-phosphate 1-dehydrogenase) and TK (Transketolase), which are key enzyme of the pentose phosphate shunt.

Overall, our data demonstrate for the first time, that the expression at diagnosis of sugar metabolic enzymes, might drive the evolutive Sokal risk of CML patients.

Supported by: European LeukemiaNet, BolognAIL, AIRC, Fondazione Del Monte di Bologna e Ravenna, FIRB 2006, PRIN 2008, Ateneo RFO grants, Project of integrate program (PIO), Programma di Ricerca Regione – Università 2007 – 2009.